I'm planning to brew a very high gravity stout. I'm expecting an OG between about 1.118 and 1.138 depending on how much my efficiency suffers. I've done this before with decent results, but I think I can provide a better fermentation than I have before.

I'm planning to mash pretty low (140-145F) so that I will have a very fermentable wort, and to minimize residual sugars.

I expect that I will want to use two yeasts; one to achieve the desired flavors (esters) and one to brave the extreme alcohol concentration and eat what it can. I'll probably stick with something like Wyeast 1272 (American Ale II) for the former; the latter I am a bit unsure about.

In the past, I've used champagne yeast, and I can't say I really had problems with it. However, even with a mash focused in the beta-amylase range, I still had a pretty sweet beer -- even after aging for a couple years. I'm wondering if another high-alcohol-tolerance yeast might attenuate a little better.

To this end, I'm considering using another yeast, like the Wyeast 775 Cider Yeast, that claims to attenuate much higher (over 80%). Wyeast even claims in its description of the yeast that it can be used for high gravity beers. In my case in particular, can a yeast really affect attenuation that much?

More subjectively, would you recommend another yeast for high alcohol fermentation?

I'm planning to ferment a bit lower to help keep excessive esters / fusel alcohols out. Something like 66F. Is this appropriate, or will I be hampering fermentation?

Lastly, should I let let the "base yeast" ferment until it has virtually stopped before pitching my high-alcohol-tolerance yeast, or should I pitch as it nears its theoretical tolerance limit? I ask because I'm concerned about the effects that might occur when the yeast hits its limit.

Edit: I'm aiming for a 10 gallon batch.

More Edit: I'm shooting for as much attenuation as possible. If I can get it up near 80, I'll be quite happy. I think I'll make a low gravity Dry Stout as a starter (5-10 gallons at about 1.040).

2 Answers
2

The different strains of yeast really do affect attenuation considerably. I've had split batches of 1.055 beer coming out with FGs of 1.007 and 1.014 just from different strains of yeast. (The lower one was US-05.)

I've not made a beer this big, but if I did, this is what I'd be thinking. As OG increases, FG increases faster since the yeast have a harder time, so getting the FG down will be the key concern. All the usual advice for big beers applies, only double.

If you want the characteristics of a specific yeast, such as the esters you mention, but also 80% attenuation, make a blend of yeasts. Choose your preferred yeast, plus a hardy, dry-fermenting, clean strain: WLP001/WY1056/US-05 are all the same strain with 80% attenuation and will go a long way to keeping down the FG. S04 is also very good and produces enough flavor that it could easily stand on it's own without needing a blend.

Since you need a lot of yeast, consider pitching on top of a yeast cake from the previous batch. Normally, this is overkill, but necessary here to ensure you have sufficient yeast.

Add nutrients, and aerate the wort very well, ideally oxygenate if you have the equipment.

66F is fine for the start of primary, you might even go lower. The temperature will need raising towards the end of primary fermentation to encourage the yeast to continue metabolizing as the environment becomes toxic.

At the end of primary, especially if the FG is higher than you like, pitch a couple of liters of actively fermenting yeast. This can reduce the FG by a few points, and cleanup the beer.

Initially, I'd stay away from the cider yeast, and wouldn't consider pitching it in primary, at least, not without doing a pilot brew first. Keep the cider yeast as a last resort if pitching fresh yeast after primary doesn't bring down the FG.

I don't think you need a "different type" of yeast for this. In addition, I've found t hat using yeasts other than beer yeast can give you strange flavors that you don't really want. The key here is going to be to pitch a large quantity of healthy yeast. I'd make a 5 gal. batch of a 1.040-50 beer and use the entire slurry from it for your stout. Keep the temps under 65F for the first week at least. While yeast type may affect attenuation a bit, the main key is wort fermentability.

Would you rack the original 5gal batch off that cake and then put your wort directly on to the yeast cake or is there some other step? Also, do you aerate the new stout or not?
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tomcoccaApr 23 '12 at 16:04

Indeed my concern with using a second yeast is the undesired flavors it might produce. If I can't get my FG where I want with my desired yeast, what would you suggest? And thanks for the input on ferm temp, I'll do my best to keep it pretty low initially.
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stepheltonApr 23 '12 at 16:51

You can either rack directly on to the slurry or remove the slurry and repitch it. Normally I wouldn't aerate when using a slurry, but given the OG of this batch it couldn't hurt to aerate.
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Denny Conn♦Apr 23 '12 at 17:48

You wouldn't aerate when using a slurry? Is that because the yeast colony is established and thus it won't go through much of an aerobic phase?
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stepheltonApr 23 '12 at 18:28

I wouldn't aerate when using a slurry because aeration is for cell growth. The yeast uses O2 to synthesize sterols for cell walls. When you pitch as huge amount of yeast there's little need for cell growth. But in a beer this big, it couldn't hurt. BTW, there really aren't distinct phases for yeast. The Crabtree Effect states that in the presence of a >.05% glucose solution, fermentation begins immediately.
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Denny Conn♦Apr 23 '12 at 18:31